Aryldiazonium cations are well known species in polar, ionizing solutions, but are almost unknown and virtually unstudied in nonpolar solutions. Solutions of these reactive species in nonpolar media may provide interesting and useful altered reactivity compared to the known chemistry in water. In an effort to achieve and understand this altered reactivity, a combination of crown ether complexation and protection of the beta-nitrogen has been and will be explored. Crown ether complexation offers the advantage that it affords excellent protection of the diazonio functional group, but the aryldiazonium compounds suffer a dramatic reduction in reactivity when so complexed. A model reaction to assess the effectiveness of certain protecting groups is cycloaddition. Aryldiazonium ions undergo cycloaddition to dienes in a few cases; crown protected aryldiazonium ions, not at all. Conversion of the aryldiazonium compound into an arenediazocyanide allows cycloaddition to become a general reaction, but clean removal of the added group is difficult. Alternative blocking groups such as phenylsulfonyl, triphenylphosphonium, etc., will be investigated for this general reactivity. A major goal of the proposed work is to achieve aromatic substitution using the aryldiazonium compounds and derivatives. This may be done either at the para position or at the ipso carbon. In the later case, metal complexes of such ligands as pyridyl-diphenylphosphine and the aryldiazonium compound should allow direct nucleophilic displacement reactions.